Improvements and microminiaturization of electronic equipment call for materials with increased dielectric constant (.epsilon.) of the order of 10 and of low loss angle at a frequency of 10.sup.10 Hz.
Glass crystalline material of the composition SiO.sub.2, Al.sub.2 O.sub.3, MgO, TiO.sub.2 with a low loss angle is known in the art. However, the dielectric constant of the known material is also small (5.5-7.5) because of the fact that titanium dioxide is precipitated not in the form of rutile (.epsilon..about.80-100) but, mainly, in solid solutions of magnesium and aluminum titanates.
Glass crystalline material containing SiO.sub.2, Al.sub.2 O.sub.3, Ca.sub.2 O, MgO and TiO.sub.2 is used as a basis for thin-film microcircuits in electronic equipment but this material cannot be used in the microwave range where losses are too high (40-45.multidot.10.sup.-4).
Also known in the art are materials based on alumina ceramics (with Al.sub.2 O.sub.3 content equal to 96-99.5%) which are used for the above-cited purposes since they possess high enough dielectric constant in combination with low loss level. However, substrates made of these materials having a high grade of surface finish (surface roughness 0.05.mu.) are rather expensive. Their cost is 5-6 times as high as that of similar items made of glass crystalline materials.
A method of producing glass crystalline material is known, wherein the initial glass is heated to maximum crystallization temperature and held at this temperature, but the rates of heating and maximum temperatures are different for various materials.